title: UVA and UVB-Induced 8-Methoxypsoralen Photoadducts and a Novel Method for their Detection by Surface-Enhanced Laser Desorption Ionization Time-of-Flight Mass Spectrometry (SELDI-TOF MS).
abstract: UVA-activated psoralens are used to treat hyperproliferative skin conditions due to their ability to form DNA photoadducts, which impair cellular processes and may lead to cell death. Although UVA (320-400 nm) is more commonly used clinically, studies have shown that UVB (280-320 nm) activation of psoralen can also be effective. However, there has been no characterization of UVB-induced adduct formation in DNA alone. As psoralen derivatives have a greater extinction coefficient in the UVB region (11 800 cm(-1)  M(-1) at 300 nm) compared with the UVA region (2016 cm(-1)  M(-1) at 365 nm), a greater extent of adduct formation is expected. SELDI-TOF, a proteomic technique that combines chromatography with mass spectrometry, was used to detect photoadduct formation in an alternating A-T oligonucleotide. 8-Methoxypsoralen (8-MOP) and DNA solutions were irradiated with either UVA or UVB. An adduct peak was obtained with SELDI-TOF. For UVB-activated 8-MOP, the extent of adducts was three times greater than for UVA. HPLC ESI-MS analysis showed that UVB irradiation yielded high levels of 3,4-monoadducts (78% of total adducts). UVA was more effective than UVB at conversion of 4',5'-monoadducts to crosslinks (17% vs 4%, respectively). This report presents a method for comparing DNA binding efficiencies of interstrand crosslink inducing agents.
authors.affiliation: Photobiology Laboratory, Hamden Hall Country Day School, Hamden, CT.
authors.forename: Alexandru D
authors.initials: AD
authors.lastname: Buhimschi
authors.affiliation: Photobiology Laboratory, Hamden Hall Country Day School, Hamden, CT.
authors.forename: Francis P
authors.initials: FP
authors.lastname: Gasparro
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry; D018736:DNA Adducts / Q000737:chemistry*; D008730:Methoxsalen / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D018736:DNA Adducts; D008730:Methoxsalen